Therapeutic versus neuroinflammatory effects of passive immunization is dependent on Aß/amyloid burden in a transgenic mouse model of Alzheimer's disease.

BACKGROUND: Passive immunization with antibodies directed to Aß decreases brain Aß/amyloid burden and preserves memory in transgenic mouse models of Alzheimer's disease (AD). This therapeutic strategy is under intense scrutiny in clinical studies, but its application is limited by neuroinflammatory side effects (autoimmune encephalitis and vasogenic edema). METHODS: We intravenously administered the monoclonal Aß protofibril antibody PFA1 to aged (22 month) male and female 3 × tg AD mice with intermediate or advanced AD-like neuropathologies, respectively, and measured brain and serum Aß and CNS cytokine levels. We also examined 17 month old 3 × tg AD female mice with intermediate pathology to determine the effect of amyloid burden on responses to passive immunization. RESULTS: The 22 month old male mice immunized with PFA1 had decreased brain Aß, increased serum Aß, and no change in CNS cytokine levels. In contrast, 22 month old immunized female mice revealed no change in brain Aß, decreased serum Aß, and increased CNS cytokine levels. Identical experiments in younger (17 month old) female 3 × tg AD mice with intermediate AD-like neuropathologies revealed a trend towards decreased brain Aß and increased serum Aß accompanied by a decrease in CNS MCP-1. CONCLUSIONS: These data suggest that passive immunization with PFA1 in 3 × tg AD mice with intermediate disease burden, regardless of sex, is effective in mediating potentially therapeutic effects such as lowering brain Aß. In contrast, passive immunization of mice with a more advanced amyloid burden may result in potentially adverse effects (encephalitis and vasogenic edema) mediated by certain proinflammatory cytokines.

Dissecting the molecular control of endothelial NO synthase by caveolin-1 using cell-permeable peptides.

In endothelia, NO is synthesized by endothelial NO synthase (eNOS), which is negatively regulated by caveolin-1 (Cav-1), the primary coat protein of caveolae. We show that delivery of Cav-1 amino acids 82-101 (Cav) fused to an internalization sequence from Antennapedia (AP) blocks NO release in vitro and inflammation and tumor angiogenesis in vivo. To characterize the molecular mechanism by which the AP-Cav peptide and Cav-1 mediate eNOS inhibition, we subdivided the Cav portion of AP-Cav into three domains (Cav-A, -B, and -C), synthesized five overlapping peptides (AP-Cav-A, -AB, -B, -BC, and -C), and tested their effects on eNOS-dependent activities. Peptides containing the Cav-B domain (amino acids 89-95) induced time- and dose-dependent inhibition of eNOS-dependent NO release in cultured endothelial cells, NO-dependent inflammation in the ear, and hydraulic conductivity in isolated venules. Alanine scanning of AP-Cav-B revealed that Thr-90 and -91 (T90,91) and Phe-92 (F92) are crucial for AP-Cav-B- and AP-Cav-mediated inhibition of eNOS. Mutation of F92 to A92 in the Cav-1 cDNA caused the loss of eNOS inhibitory activity compared with wild-type Cav-1. These data highlight the importance of amino acids 89-95 and particularly F92 in mediating eNOS inhibition by AP-Cav and Cav-1.